Motor

ABSTRACT

In a permanent magnet-embedded, concentrated winding motor, plurality of stator teeth are divided into, for example, three groups that include a plurality of adjacent stator teeth having coils wound around and that are provided with voltage in phase that are set as one group. Coils are wound in opposite directions around adjacent stator teeth in the same group, while the relation between the angle h of a slot opening between adjacent stator teeth of the same group and the angle H of a slot opening formed between adjacent stator teeth of different groups satisfies h&lt;H≦3h.

TECHNICAL FIELD

The present invention relates to a motor suitably applied to a vehiclesuch as a pure electric vehicle (PEV), a hybrid electric vehicle (HEV),and a fuel cell electric vehicle (FCEV), and also to a motor suitablyapplied to a home electrical appliance, a robot, and the like.

BACKGROUND ART

As motor technology for use in a vehicle and the like as describedabove, Japanese Patent Laid-Open Publication No. 2000-245085 disclosesthe use of a concentrated winding, magnet-embedded type motor.

The example disclosed by Japanese Patent Laid-Open Publication No.2000-245085 will be described in conjunction with FIG. 17. FIG. 17 is asectional view of a main part of a motor including a concentratedwinding stator made of a stator core, a plurality of stator teeth withcoils wound therearound, and a magnet-embedded type rotor. The sectionis a plane orthogonal to the central axis of the rotating shaft of themotor.

As shown in FIG. 17, the stator core 145 includes a plurality of statorteeth 143 a, 143 b, and 143 c, and a stator yoke 144 coupling them.Coils 146 a, 146 b, and 146 c are wound around the stator teeth 143 a,143 b, and 143 c, respectively and thus the stator 146 is formed. Amongthe stator teeth 143 a, 143 b, and 143 c, the stator tooth 143 a isformed on one side of the stator tooth 143 b, the stator tooth 143 c isformed on the other side, and thus one group is formed. Groups of suchstator teeth 143 a, 143 b, and 143 c are provided in the circumferentialdirection. The stator teeth 143 a each have a coil 146 a woundtherearound in parallel, the end of the wound coil 146 a is connectedwith a common terminal (not shown), and a single terminating connectionline is drawn from the common terminal. The stator teeth 143 b each havea coil 146 b wound therearound in parallel, and the stator teeth 143 ceach have a coil 146 c wound therearound in parallel. The terminatingconnection lines for the stator teeth 143 a, 143 b, and 143 c are eachconnected to another common terminal (not shown).

The rotor 147 has a plurality of permanent magnets 149 embedded at equalintervals in the circumferential direction so that these magnets opposethe inner circumferential surfaces of the stator teeth 143 a, 143 b, and143 c of the stator 146. The rotor 147 has its outer circumferentialsurface opposed to the inner circumferential surfaces of the statorteeth 143 a, 143 b, and 143 c of the stator 146 with a very small gaptherebetween. The distance between the surfaces 149 a of the permanentmagnets 149 that oppose the inner circumferential surfaces of the statorteeth 143 a, 143 b, and 143 c and the outer circumferential surface ofthe rotor 147 is larger toward the central part 149 c than at the ends149 b of the permanent magnet 149.

The coils 146 a, 146 b, and 146 c form three phases, or a U phase, a Vphase, and a W phase, respectively, and when currents in trapezoidalwaveforms for example 120 electrical degrees out of phase between eachother are provided to the coils in these phases, and torques generatedbetween the coils 146 a, 146 b, and 146 c in these phases and the rotor147 are 120 degrees out of phase between each other. The torques in thethree phases are combined to form a total torque, and the rotor 147rotates in a prescribed direction accordingly. More specifically,so-called three phase, full wave-driven rotation around the center O ofthe rotating shaft is carried out. Therefore, in addition to themagnetic torque resulting from the embedded permanent magnets 149 in therotor 147, a reluctance torque can also be used, so that a high output(high torque) motor that generates a large torque can be provided.

Meanwhile, when the rotor 147 is driven to rotate, a counterelectromotive voltage in a substantial sine wave is generated between acommon terminal (not shown) and the U, V, and W phase terminalsaccording to the Flemming's right hand rule. As is well known, thecounter electromotive voltages for the phases are 120 electrical degreesout of phase among each other, and the counter electromotive voltages inthe different phases are combined to obtain a total counterelectromotive voltage.

For environmental concerns and resource conservation, there is a demandfor use of less copper coils in vehicle motors in general. In theprocess of recycling automobiles, motors with copper wires mixed withother motors deteriorate the quality level of recycled iron, and in thefield of automobiles, motors with copper-free wires are stronglydesired. According to conventional techniques, aluminum wires are usedfor coils for motors instead of copper wires, or aluminum wires are usedfor other general commutator coils instead of copper wires as disclosedby Japanese Patent Laid-Open Publication No. 2000-245085. However,examples of actual application of the disclosed methods to automobileshave not been known.

The motor with a large torque including the additional reluctance torquecan advantageously have a high torque by employing a concentratedwinding motor. On the other hand, waveform distortions are observed inthe counter electromotive voltage.

A large waveform distortion in the counter electromotive voltageincreases eddy current and thus iron loss, which lowers the efficiency.Eddy current is also generated at the permanent magnets embedded in therotor, and the permanent magnets generate heat to have increasedtemperature, and could be demagnetized.

Therefore, it is a first object of the invention to provide a hightorque, high efficiency motor in a structure with reduced waveformdistortions in the counter electromotive voltage and with reduced eddycurrent generation.

Meanwhile, if coils for a motor as disclosed by Japanese PatentLaid-Open Publication No. 2000-245085, a typical commutator motor and abrushless motor are simply changed from copper wires to aluminum wires,the conductor loss could be great because the resistivity of thealuminum wire is higher than copper wire by about 60%. Therefore, theefficiency of the motor is lowered. Meanwhile, in order to keep the lossfrom increasing, the motor size must be increased, and in either way,the method remains to be disadvantageous in terms of energy and resourceconservation.

It is a second object of the invention to provide a motor with coilsmade of aluminum or another metal having resistivity larger than copperinstead of copper without increasing the size of the motor and loweringthe efficiency while the first object is achieved as well.

DISCLOSURE OF THE INVENTION

In order to achieve the above-described object, a motor according to theinvention includes: a stator including a stator core having a pluralityof stator teeth, and a stator yoke that connects the plurality of statorteeth, and coils wound around the plurality of stator teeth; and a rotorincluding a rotor core, and a plurality of permanent magnets embedded inthe rotor core, wherein groups made of the plurality of adjacent statorteeth around which the coils are wound around are provided. The coilsare provided with voltage in phase, coils are wound in oppositedirections around the plurality of adjacent stator teeth in the samegroup, and voltage in different phases are applied to the adjacentgroups.

In this way, since the permanent magnets are embedded in the rotor, areluctance torque as well as a magnet torque will be used, and a hightorque will be generated. Furthermore, the coils for adjacent statorteeth in each group are wound so that they have different polaritiesfrom each other, which alleviate deviations in the magnetic fielddistribution and reduce distortions in the waveform of counterelectromotive voltage induced at the coils at the time of driving themotor. Therefore, the iron loss in the stator core and the rotor coreare restrained, and eddy current is restrained for the permanent magnetsin the rotor core. Since eddy current is reduced, heat generation by theeddy current will be alleviated, and the permanent magnets are preventedfrom demagnetizing. Therefore, an efficient motor is provided.

In the above-described motor, the stator teeth of the stator are dividedinto 3n (n: positive integer) groups, each of which has three statorteeth. In this way, adjacent coils in the U, V, and W phases in eachgroup have different polarities, and deviations in the magnetic fielddistribution are alleviated, so that distortions in the waveform of thevoltage between the terminals at the time of driving are reduced.Therefore, the iron loss will be restrained, which improves the motorefficiency.

In the above-described motor, the relation represented by the followingexpression is satisfied for the angle h of a slot opening formed betweenadjacent stator teeth in the same group and the angle H of a slotopening formed between adjacent stator teeth belonging to differentgroups:

-   -   h<H≦3h.

In this way, the magnetic field distribution is homogeneous, so thatwaveform distortions in the counter electromotive voltage is reduced,eddy current is reduced to reduce the iron loss, and heat generation bythe eddy current at the permanent magnets is then reduced.Demagnetization of the magnets is also reduced. Consequently, the motorefficiency will be improved.

Furthermore, in the above-described motor, a central line passingthrough each of the circumferential centers of the tip ends of statorteeth in each group positioned at both ends of said group adjacent tostator teeth belonging to different groups is deviated in thecircumferential direction from a central line passing through each ofthe circumferential centers of the parallel parts of the stator teethpositioned at both ends in said group. The circumferential ends at saidtip ends are not positioned inward in the width-wise direction of theparallel parts in either direction.

In this way, the slots between the stator teeth are formed to be spacesin substantially equal sizes, so that the number of turns at coils woundaround the stator teeth increases, and the generation torque isincreased according to the increase in the number of turns. Meanwhile,adjacent coils in the same group have different polarities, so thatdistortions in generation voltage will be restrained, and therefore theiron loss will be reduced. Consequently, it becomes possible to providea very efficient motor.

In the above-described motor, cuts are provided in the plurality ofstator teeth forming the stator core so that the distance between thestator opposing surface of the rotor and the rotor opposing surface ofthe stator teeth at the tip end is greater in the vicinity of thecircumferential ends of said tip ends. In this way, abrupt changes inthe magnetic field at the stator teeth is alleviated, so that thewaveform of counter electromotive voltage generated at the coil at thetime of driving the motor will be more approximated to a sine waveform,and torque ripple and cogging torque will be reduced.

In the above described motor, in the stator core, the tip end of atleast one of the stator teeth forming the plurality of groups on theside of the rotor is provided with at least one recess. The recess has asubstantially rectangular or arc shape. It is understood that othershapes may be employed.

In this way, the magnetic poles at the tip ends of these stator teethare divided into S, N, and S poles in appearance, a high torque will beprovided, and torque ripple will be reduced to a small level.

In the above-described motor, a side surface of the stator yoke on theside opposite to the rotor side in the stator core is in a shapeprotruding more onto the opposite side to the rotor side beyond a circleinscribed to each side surface of the stator yoke on a side surface onthe opposite side to the rotor side of the plurality of stator teeth,and the width w of the stator yoke is equal for the entirecircumference. Furthermore, the relation between the width w of thestator yoke and the width W of the parallel part of the stator tootharound which a coil is wound is represented by the following expression:W×½≦w≦W× 3/2.

In this way, the magnetic resistance becomes well balanced, and asubstantially homogeneous flux is generated. Consequently, a stable andefficient magnetic field will be provided.

In the above-described motor, the rotor has a plurality of permanentmagnets and a plurality of slits on the opposite side to the stator sideof the permanent magnets. Each of the plurality of slits hassubstantially the same shape as that of the permanent magnet and a widthsmaller than the thickness of the permanent magnet.

In this way, a magnetic flux generated at the permanent magnets are lesseasily passed at the slits, in other words, the magnetic resistancethere is increased, d-axis inductance is reduced, and the differencebetween the d-axis inductance and the q-axis inductance is increased. Inthis way, a larger reluctance torque will be generated, so that thetorque generated by the motor will be increased.

In the above-described motor, the rotor is provided with a plurality ofpermanent magnets each having a shape in such a manner that the distancebetween the stator side surface of each of the plurality of permanentmagnets and the stator opposing surface of the rotor is larger towardthe central part than at the ends of each of the permanent magnets. Inaddition, the permanent magnets are in a substantially V shape thatprotrudes in a direction opposite to the side of the stator opposingsurface of the rotor. Alternatively, the rotor is provided with aplurality of permanent magnets in a linear shape perpendicular to theradial direction of the rotor. Alternatively, the rotor is provided witha plurality of permanent magnets in an arc shape that protrudes in adirection opposite to the stator opposing side of the rotor.Alternatively, the rotor is provided with a plurality of permanentmagnets in an arc shape that protrudes toward the stator opposingsurface and has a radius greater than the radius of the rotor core.

In this way, there are a part that relatively easily passes a magneticflux and a part that less easily passes a magnetic flux, in other words,parts with low magnetic resistance and high magnetic resistance areprovided, so that difference is produced between the inductance in theq-axis direction and d-axis direction. Thus, a reluctance torque will begenerated, and an increased torque will be generated.

The above-described motor is related to a technique of increasing thenumber of poles for a motor, in the relation between the number of polesat the rotor portion and the number of tooth poles at the stator portionto be provided with a coil, as compared, for example, to four poles andtwelve tooth poles for a typical brushless motor, the number of poles islarger as there are ten poles and nine tooth poles, but the number oftooth poles is reduced despite the increased total number of poles.

The motor torque is determined as:(Motor torque)=(the number of rotor pole pairs)×(the number ofinterlinked magnetic fluxes)×(motor current).Therefore, in the motor, the number of rotor poles is increased, and yetthe number of stator tooth poles is not increased, in other words, themotor current is not decreased.

Furthermore, since the widths of the slot opening and stator teeth areset as described above, the waveform of the counter electromotivevoltage will be approximated to a sine wave with a large torque ascompared to a conventional motor in the same size, and an aluminum wirewill then be used for the coil instead of a copper wire withoutincreasing the size of the above-described motor and without increasingdistortions in the waveform of the counter electromotive voltage ascompared to the conventional motor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view of a main part of a motor accordingto Embodiment 1 of the present invention for use in illustration of themotor main part;

FIG. 2 is a schematic development for use in illustration of thedirection in which coils are wound according to the Embodiment 1 of thepresent invention;

FIG. 3 is a view showing how coils are connected according to theEmbodiment 1 of the present invention;

FIGS. 4A to 4C are schematic sectional views of other examples of thepermanent magnets according to the Embodiment 1 of the presentinvention, and FIG. 4D is a schematic sectional view of another exampleof the rotor core according to the Embodiment 1 of the presentinvention;

FIG. 5 is a schematic sectional view of a stator core according toEmbodiment 2 of the present invention for use in illustration of thestator core;

FIG. 6A is a partially enlarged view for use in illustration of thestator core according to the Embodiment 2 of the present invention, andFIG. 6B is a partially enlarged view for use in illustration of amodification of the stator core according to the same embodiment;

FIG. 7 is a partially enlarged view for use in illustration of anexample of the shape of a stator tooth that is not suitable for thepresent invention;

FIG. 8 is a schematic sectional view for use in illustration of a mainpart of a motor according to Embodiment 3 of the present invention;

FIG. 9 is a partially enlarged view for use in illustration of a statorcore according to the Embodiment 3 of the present invention;

FIG. 10A is a schematic top view for use in illustration of a statorcore according to Embodiment 4 of the present invention, FIG. 10B is apartial view of another example of the recess according to the sameembodiment, and FIG. 10C is a partial view of the shape of yet anotherexample of the recess according to the same embodiment;

FIG. 11 is a schematic sectional view for use in illustration of astator core according to Embodiment 5 of the present invention;

FIG. 12 is a schematic sectional view for use in illustration of a mainpart of a motor according to Embodiment 6 of the present invention;

FIG. 13 is a schematic sectional view for use in illustration of a mainpart of a motor according to Embodiment 7 of the present invention;

FIG. 14 is a schematic sectional view of an aluminum coil according toEmbodiment 8 of the present invention;

FIG. 15A is a schematic view of an end of the aluminum coil according tothe Embodiment 8 of the present invention, and FIG. 15B is a schematicview of another example of the aluminum coil end according to the sameembodiment;

FIG. 16A is a schematic view showing how lead wires and aluminum coilsaccording to Embodiment 10 of the present invention are connected, FIG.16B is a schematic view of another example of how lead wires andaluminum coils according to the same embodiment are connected, and FIG.16C is a schematic view of yet another example of how lead wires andaluminum coils according to the same embodiment are connected; and

FIG. 17 is a schematic sectional view of a main part of a conventionalmotor.

BEST MODE FOR CARRYING OUT THE INVENTION

Now, an embodiment of the present invention will be described inconjunction with the accompanying drawings.

Embodiment 1

FIGS. 1 to 4D are views for use in illustration of a motor according toEmbodiment 1 of the present invention. FIG. 1 is a sectional view of amain part in a plane orthogonal to the central axis of the rotatingshaft for the purpose of illustrating the motor main part, FIG. 2 is adevelopment for use in illustration of the direction in which coils arewound around stator teeth, FIG. 3 is a view for use in illustration ofhow coils wound around stator teeth are connected, and FIGS. 4A to 4Dare sectional views of the shapes of permanent magnets embedded in rotorcores and other examples of the rotor cores.

In FIG. 1, a stator core 1 includes a plurality of stator teeth 2 a, 2b, 2 c, 3 a, 3 b, 3 c, 4 a, 4 b, and 4 c, and a stator yoke 5 thatconnects the stator teeth 2 a to 4 c at one end. A coil 6 is woundaround each of the stator teeth 2 a to 4 c, and the stator core 1 andthe coils 6 form a stator 7.

The stator teeth 2 a to 4 c are divided into three groups in total, eachof which has a plurality of adjacent stator teeth having coils woundaround to be provided with voltage in phase. More specifically,according to the embodiment, there are a first group 2 having statorteeth 2 a, 2 b, and 2 c, a second group 3 having stator teeth 3 a, 3 b,and 3 c, and a third group 4 having stator teeth 4 a, 4 b, and 4 c. Asfor the angles of the openings of the slots formed between the adjacentstator teeth, the slot opening of a slot 6 a formed between the statorteeth 2 a and 2 b adjacent to each other in the first group 2 will bedescribed as an example. The letter h represents the angle between thetangents 2 at and 2 bt in contact with the ends at the tip of the statorteeth 2 a and 2 b projecting in the circumferential direction on theopposite side to the stator yoke and passing the center O of therotating shaft. Similarly, the angles of the other slot openings areeach the angle between tangents passing the center O of the rotatingshaft and in contact with the opposing ends on the slot side.

The angles of the slot openings between the stator teeth 2 b and 2 c,between the stator teeth 4 a and 4 b, between the stator teeth 4 b and 4c, between the stator teeth 3 a and 3 b, and between the stator teeth 3b and 3 c are each set to be equal to the slot opening angle h betweenthe stator teeth 2 a and 2 b. Meanwhile, the angle of a slot opening 6 bbetween the adjacent stator teeth 3 c and 2 a belonging to differentgroups is H. Similarly, the angles of the slots between the stator teeth2 c and 4 a and between the stator teeth 4 c and 3 a are set to be equalto the angle H of the slot opening between the stator teeth 3 c and 2 a.Note that the angle H is larger than the angle h of the slot openingbetween adjacent stator teeth belonging to the same group as describedabove.

The coil 6 wound around each of the stator teeth 2 a to 4 c will bedescribed with reference to the group 2 as an example. As shown in FIG.2, when the coil 6 is wound around the stator tooth 2 a in the directiondenoted by the arrow 21, the coil 6 is wound around the stator tooth 2 bin the direction denoted by the arrow 22 that is opposite to thedirection of the arrow 21, and the coil 6 is wound around the statortooth 2 c in the direction denoted by the arrow 23 that is opposite tothe direction of the arrow 22, in other words, the same as the arrow 21.More specifically, the coils are wound around the stator teeth in eachgroup in opposite directions for adjacent stator teeth in the group towhich the stator teeth belong, so that the adjacent stator teeth havepolarities inverted from each other. The coils 6 are wound around thestator teeth 2 a, 2 b, and 2 c in parallel. It is understood that thecoils may be wound in series. Similarly, the coils 6 are wound aroundthe stator teeth included in the groups 3 and 4 in the same manner, sothat the coils 6 in the groups 2, 3, and 4 are to be coils in threephases, U, V, and W phases, respectively. When, for example, the coil 6for the stator tooth 2 a in the group 2 is in the U phase, the coil 6for the adjacent stator tooth 2 b having a polarity inverted from thatof the coil 6 for the stator tooth 2 a is in the inverted U phase, andthe coil 6 for the stator tooth 2 c adjacent to the stator tooth 2 b isin a phase inverted from the phase of the coil 6 for the stator tooth 2b, in other words, in the U phase that is the same as the phase of thestator tooth 2 a. This applies to the coils for the stator teeth in thegroups 3 and 4, and the phases are the V phase and the inverted V phase,and the W phase and the inverted W phase, respectively. Furthermore, theend of winding of the coils 6 for the groups 2, 3, and 4 are connectedas shown in FIG. 3. Note that in FIG. 3, 15 u, 15 v, and 15 w are theoutput ends in the U, V, and W phases, respectively, 16 represents themid point, and 17 is a line connecting the coils 6. In the abovedescribed manner, the adjacent coils in the U, V, and W phases in eachgroup have polarities different from each other, so that deviations inthe magnetic field distribution is alleviated, and waveform distortionsin counter electromotive voltage generated between terminals at the timeof driving the motor is reduced, so that the iron loss is reduced.

As a result of further study, when the relation represented by thefollowing expression is satisfied for the angle h of the slot openingformed between adjacent stator teeth in the same group and the angle Hof the slot opening formed between adjacent stator teeth belonging todifferent groups,h<H≦3h  (1)the magnetic field distribution is homogeneous, so that waveformdistortions in the counter electromotive voltage is reduced, eddycurrent is reduced to reduce the iron loss, and heat generation by theeddy current at the permanent magnets is reduced. In this way,demagnetization of the magnets will be reduced. Consequently, the motorimproves efficiency.

Meanwhile, a rotor 8 includes a rotor core 9 and a plurality ofsubstantially V-shaped permanent magnets 10 embedded in the rotor core 9at equally spaced intervals in the circumferential direction, the statoropposing surface of the rotor 8 opposes the rotor opposing surface ofthe stator 7 with a very small gap therebetween. The rotor is rotatablearound the center O of the rotating shaft.

The permanent magnets 10 are substantially in a V-shape that protrudesin the direction opposite to the stator opposing surface of the rotor 8,the distance between the stator side surface 10 a of the permanentmagnet 10 and the stator opposing surface 8 a of the rotor 8 is largertoward the central part 10 d than at the ends 10 b and 10 b on thestator side surface 10 a of the permanent magnet 10. Therefore, thereare a part that relatively easily passes a magnetic flux and a part thatless easily passes a magnetic flux on the stator opposing part of therotor 8. More specifically, the parts with low magnetic resistance andhigh magnetic resistance are provided, so that difference is producedbetween the inductance in the q-axis direction and d-axis direction.Thus, a reluctance torque is generated, and then torque generation isincreased.

The shape of the permanent magnet 10 may be any shape as long as thedistance between its side surface 10 a and the stator opposing surface 8a of the rotor 8 is larger toward the central part than at the end part.For example, the permanent magnet may be a linear shaped permanentmagnet 31 arranged perpendicularly to the radial direction as shown inFIG. 4A, an arc permanent magnet 32 curved outwardly in the directionopposite to the stator side as shown in FIG. 4B or an arc permanentmagnet 34 curved outwardly to the stator side and having a radius equalto or larger than the radius of a rotor core 33 as shown in FIG. 4C.Furthermore, as shown in FIG. 4D, a rotor 38 may include a rotor core 35having permanent magnets 36 embedded therein and slits 37 provided moreon the side opposite to the stator side (not shown) than the permanentmagnets 36 and having a shape substantially the same as that of thepermanent magnet 36 and a width 37 a smaller than the thickness 36 a ofthe permanent magnet 36. Since the slits are provided near the permanentmagnets, it is difficult for a magnetic flux generated by the permanentmagnets to pass at the slit location, so that the d-axis inductance isreduced and the difference between the d-axis inductance and the q-axisinductance is increased, and that a large reluctance torque isgenerated. Consequently, the torque generated by the motor increases. Itis understood that for the rotor core 35 with the slits, the shape ofthe permanent magnet may be a linear shape or an arc shape curvedoutwardly to the stator side or the opposite side, as shown in FIGS. 4Ato 4C.

Note that according to Embodiment 1, the number of slots formed betweenthe plurality of stator teeth is nine (as many as the number of thestator teeth), the number of the permanent magnets forming the rotor isten, the number of sets of coils is one as coils in three phases U, V,and W phases are counted as a set. The number of stator teeth per groupis three. More specifically, Embodiment 1 is related to a motor withthree stator teeth per group, one set of coils, nine slots, and tenpoles. The invention is not limited to the motor with three stator teethper group, one set of coils, nine slots, and ten poles, and is alsoapplicable to a motor with n stator teeth per group, s sets of coils, tslots and p poles (where n, s, t, and p are all a positive integer).Note in this case, the number of rotor poles p satisfies the followingexpression:P=2×(s(±1+3k)) and p>t(where k is a positive integer)  (2)

Here, why the number of poles is determined as described above will bedescribed. One characteristic of the motor according to the inventionresides in that the pitch between the magnets and the teeth pitch in thestator are the same, and there is a dead space in the stator. Therefore,once the number of teeth per group and the number of sets of coils aredetermined, the number of poles may be mechanically provisionallydetermined. For example, in a model of “two stator teeth per group andone set of coils” in a three-phase motor, the number of slots (t) isproduced by the number of teeth per group (n)×the number of phases×thenumber of sets of coils (s), in other words, the number of slots(t)=2×3×1=6. Since the number of slots (t) is six, in order to securethe dead space, the number of poles (p) is an even number equal to orlarger than eight based on the above expression (2).

Now, the number of slots and the number of poles provisionallydetermined are used to determine if the motor functions as a motor. Morespecifically, it is determined whether the motor smoothly rotates whencurrent is passed in the order of the U phase, V phase, and W phase.When the number of pole pairs for the magnet is p/2, the inductivevoltage function for the magnet will be represented as follows:Be=sin(p/2×θ)

Now, since the motor is a three-phase motor, the U, V, and W phases areshifted at intervals of 120 electrical degrees. Therefore, when currentis passed through these phases, as the current is 120 electrical degreesshifted from each other, the rotor needs only be rotated for the sameelectrical angle in the same direction. In other words, the followingexpression should be satisfied.sin(p/2×(θ+120/s))=sin(p/2×θ±120+360 k)  (3)

The above expression (3) indicates that when the inductive voltagefunction (rotor) is positioned 120 electrical degrees shifted from acertain time point Be=0 (the expression is based on mechanical angle),and this position is the same as the position 120° (the deviation amongthe U, V, and W phases) shifted on another axis on the stator side,current passed from the U phase to the V phase or from the V phase tothe W phase in other words between positions 120° shifted from eachother allows the rotor position Be (inductive voltage function) toalways take the same electrical value, and the motor smoothly rotatesonce.

The above expression (3) is expressed as follows for the pole pairnumber p/2.p/2=s(±1+3 k)

The pole number (p) is expressed as a function of the coil set number(s) as follows:p=2×(s(±1+3k))

Using this expression, the number of poles is determined. Note thatspecific examples are given in the following table.

number of teeth number of number of number of per group coil sets slotspoles 2 1 6 8 2 2 12 16 2 3 18 24 2 4 24 32 3 1 9 10 3 2 18 20 3 3 27 303 4 36 40 4 1 12 14 4 1 12 16 4 2 24 28 4 2 24 32 5 1 15 16 5 1 15 20 51 15 22 5 2 30 32 5 2 30 40 6 1 18 20 6 1 18 22 6 1 18 26 6 2 36 40 7 121 22 7 1 21 26 7 1 21 28

As in the foregoing, according to the Embodiment 1, among the statorteeth of the stator, adjacent stator teeth having coils wound around tobe provided with voltage in the same phase are counted as one group, andthe stator teeth are divided into three groups for the U, V, and Wphases. The coils are wound in the opposite directions around adjacentstator teeth belonging to the same group, while the distance between thestator side surface of the plurality of permanent magnets embedded inthe rotor and the stator opposing surface of the rotor is larger towardthe central part than at the end side of the permanent magnets. In thisway, a reluctance torque is used in addition to the magnet torque, sothat a high torque is generated. Distortions in the generated voltageare reduced, which reduces the iron loss and restrains the permanentmagnets from being demagnetized. Consequently, a very efficient motorwill be provided.

Embodiment 2

FIGS. 5 to 7 are views for use in illustration of a motor according toEmbodiment 2 of the present invention, FIG. 5 is a top view of a statorcore, FIG. 6A is a partially enlarged view showing a part of FIG. 5being enlarged, FIG. 6B is a partially enlarged view showing a part of amodification of the stator core being enlarged, and FIG. 7 is a enlargedview showing a modification of the tip end of a stator tooth.

In FIG. 5, a stator core 41 includes stator teeth 42 a, 42 b, 42 c, 43a, 43 b, 43 c, 44 a, 44 b, and 44 c, and a stator yoke 45 that connectsthese stator teeth 42 a to 44 c at one end. Similarly to Embodiment 1,the stator teeth 42 a, 42 b, and 42 c form a group 42, the stator teeth43 a, 43 b, and 43 c form a group 43, and the stator teeth 44 a, 44 b,and 44 c form a group 44. The coils (not shown) wound around the statorteeth in the groups 42, 43, and 44 form U, V, and W phases,respectively. Similarly to Embodiment 1 described above, the directionsin which coils are wound around adjacent teeth in the same group areinverted, and the relation between the angle h of a slot opening betweenadjacent stator teeth in the same group and the angle H of a slotopening formed between adjacent stator teeth belonging to differentgroups satisfies the foregoing expression (1).

The slots between the stator teeth are formed to be spaces havingsubstantially equal sizes, so that the number of turns at coils woundaround the stator teeth will be increased, and the generation torquewill then be increased according to the increase in the number of turns.

Now, with reference to the group 42 described above, the shape of thestator teeth 42 a, 42 b, and 42 c at their tip ends will be descried inconjunction with FIG. 6A.

FIG. 6A is a partially enlarged view showing the group 42 in the statorcore 41. In FIG. 6A, θ represents the angle formed by the central line51 passing through the circumferential center of the parallel part ofthe stator tooth 42 a and the center O of the rotating shaft and thecentral line 52 passing through the circumferential center of theparallel part of the stator tooth 42 b and the center O of the rotatingshaft. The letter φ represents the angle between the central line 53passing through the circumferential center of the tip end of the statortooth 42 a and the center O of the rotating shaft and the central line52 passing through the circumferential center of the parallel part ofthe stator tooth 42 b and the center O of the rotating shaft. The letterα represents the angle between the line 54 passing through the side ofthe parallel part of the stator tooth 42 a opposite to the stator tooth42 b, the angular portion 56 at the tip end, and the center O of therotating shaft, and the central line 51 in the stator tooth 42 a. Theletter β represents the angle between the line 55 in contact with thecircumferential end at the tip of the stator tooth 42 a opposite thestator tooth 42 b and the center O of the rotating shaft and the centralline 53 passing through the circumferential center of the tip of thestator tooth 42 a and the center O of the rotating shaft. The centralline 51 of the parallel part in the stator tooth 42 a and the centralline 53 passing through the circumferential center of the tip end of thestator tooth 42 a are deviated from each other. More specifically, therelation represented by (φ+β)>(θ+α) is satisfied. Meanwhile, the otherstator tooth 42 c in the group 42 has a shape symmetric to the statortooth 42 a with respect to the central line 52 of the stator tooth 42 b.

In general, the widths of the parallel parts around which the coils forthe stator teeth are wound are formed to be substantially equal so thatthe density of magnetic fluxes generated by the coils is substantiallyequalized. Consequently, in order to substantially equalize the spacesformed between the stator teeth, in other words, to equalize the sizesof the slot spaces, the following expression should be established.θ=θ_(o)=360/n°(n: the number of slots)=360/9° (n=9 in Embodiment 2)=40°

Meanwhile, FIG. 6B is a partially enlarged view showing a modificationof the stator core shape. In FIG. 6B, the basic configuration is thesame as that described in conjunction with FIG. 6A, and in themodification, the tip end shape of the stator teeth 61 a and 61 c isdifferent from that of the foregoing example protruding toward bothcircumferential sides described above and does not project in thecircumferential direction on the opposite side of the stator tooth 61 b.More specifically, the shape conforms to the side of the parallel part.In this way, a line 68 passing through the front most tip 67 of theparallel part of the stator tooth 61 a on the side surface opposite tothe stator tooth 61 b and the center O of the rotating shaft and atangent line 68 in contact with the circumferential end of the statortooth 61 a on the opposite side to the stator tooth 61 b and passingthrough the center O of the rotating shaft are the same. In thisconfiguration, their angular relation is represented as (φ+β)=(θ+α).Then, the central lines 64 a and 64 b passing through thecircumferential centers of the tip ends of the stator teeth 61 a and 61c, respectively (which are symmetric with respect to the central line 63passing through the circumferential center of the stator tooth 61 b andthe center O of the rotating shaft) and the center O of the rotatingshaft are deviated from the central lines 62 a and 62 b passing throughthe circumferential centers of the parallel parts of the stator teeth 61a and 61 c, respectively and the center O of the rotating shaft.Therefore, the slot spaces 66 between the stator tooth 61 b and theadjacent stator teeth 61 a and 61 c have the same volume and arerelatively large. Therefore, the number of turns in the coils isincreased. Note that in this case, the relation between the angle h of aslot opening between adjacent stator teeth in the same group and theangle H of a slot opening formed between adjacent stator teeth belongingto different groups satisfies the foregoing expression (1) according tothe Embodiment 1 described above.

The shape of the tip end of the stator teeth in the other groups shouldbe the shape that satisfies the relation represented by (φ+β)>(θ+α) bythe same method applied to the stator teeth 42 a to 42 c. When a motorhaving stator teeth in the shape of the stator teeth 61 a to 61 c isformed, the shape of the tip ends of the stator teeth in the othergroups needs only satisfy the relation represented by (φ+β)=(θ+α).

However, when a stator tooth having a shape as shown in FIG. 7 isformed, the circumferential center of the tip end of the stator tooth 55a is deviated from the circumferential center of the parallel part ofthe stator tooth 55 a, but the side surface 56 a of the parallel partextends beyond the circumferential projection 57 a of the tip end in thecircumferential direction. More specifically, (φ+β)<(θ+α) stands, andthe area of the boundary part 58 between the parallel part and the tipend part of the stator tooth 55 a is reduced. When the area of theboundary part 58 is reduced, a magnetic flux 59 generated at the statortooth 55 a is concentrated and more easily saturated, and the directionof the magnetic flux 59 changes abruptly. Therefore, the magneticresistance increases at the boundary part 58 with the abrupt change andthe flow of magnetic flux is inefficient. Therefore, the configurationthat allows the deviation relation between the parallel part and the tipend part to be represented by (φ+β)<(θ+α) is not preferable.

In the configuration similar to that of the Embodiment 1 describedabove, a stator includes a stator core and coils arranged around aplurality of stator teeth, a rotor rotates around the center of therotating shaft with a very small gap apart from the rotor opposingsurface of the stator, the rotor includes a rotor core and a pluralityof permanent magnets embedded in the rotor core at equally spacedintervals in the circumferential direction, and the stator opposingsurface of the rotor opposes the rotor opposing surface of the stator.

Note that according to the embodiment, a motor has three stator teethper group as an example, but as described in conjunction with theEmbodiment 1, the invention is applicable to a motor with n stator teethper group (n: positive integer). In the case, regardless of whether thenumber of teeth per group is an even number or an odd number, only twostator teeth at both ends of a group, in other words, only two statorteeth belonging to the same group and yet each adjacent to a statortooth in another group should have a shape in which a central linepassing through the circumferential center of the tip end is deviatedfrom the central line of the parallel part. Note that in this case, thecentral line passing through the circumferential center of the tip endand the central line passing through the circumferential center of theparallel part are preferably deviated within the range of (φ+β)≧(θ+α).

As described above, according to Embodiment 2, similarly to theembodiment described above, a plurality of stator teeth are divided intothree groups. In the same group, the central lines through the parallelparts having coils wound around in the stator teeth adjacent to thestator teeth in the center of the group that passes through the centerof the rotating shaft are deviated from the central lines passingthrough the circumferential center of the tip end parts of the statorteeth opposite to the stator yoke and the center of the rotating shaft.In this way, the slot spaces formed by the adjacent stator teeth areincreased, and the number of turns in coils around the stator teeth isalso increased. Similarly to the Embodiment 1 described above, the rotorhaving a plurality of embedded permanent magnets (hereinafter simplyreferred to as the “permanent magnet-embedded rotor”) has a shape suchthat the distance between the stator opposing surface of the rotor andthe stator side surface is greater on the central part than on the endpart of the stator side surface. In this way, a reluctance torque isadded to the magnet torque then a higher torque will be generated. Inthe same group, coils are wound in the opposite directions aroundadjacent stator teeth, so that distortions in the generated voltage arereduced, which reduces the iron loss, and a very efficient motor will beprovided.

Embodiment 3

FIGS. 8 and 9 are views for use in illustration of a motor according toEmbodiment 3 of the present invention. FIG. 8 is a schematic sectionalview of a stator core and a rotor opposing the inner circumferentialsurface of the stator core taken along a plane perpendicular to thecentral axis of the rotating shaft and FIG. 9 is a partially enlargedview showing a stator core being enlarged for the purpose of showing theshape of stator teeth forming the stator core.

In FIG. 8, a stator core 71 includes stator teeth 72 a, 72 b, 72 c, 73a, 73 b, 73 c, 74 a, 74 b, and 74 c, and a stator yoke 75, and similarlyto the Embodiment 1 described above, the plurality of stator teeth 72 ato 74 c are divided into three groups 72, 73, and 74. In the same group,coils 76 are wound around adjacent stator teeth in opposite directionsto each other. The stator core 71 and the coils 76 arranged around thestator teeth 72 a to 74 c of the stator core 71 form the stator 77.There is a small gap between the rotor opposing surface at the tip endof the stator teeth on the opposite side to the stator yoke and thestator opposing surface of the permanent magnet embedded rotor 78 thatrotates around the center O of the rotating shaft. Similarly to theEmbodiment 1 described above, the relation between the angle h of a slotopening between adjacent stator teeth in the same group and the angle Hof a slot opening formed between adjacent stator teeth belonging todifferent groups satisfies the foregoing expression (1).

FIG. 9 is a partly enlarged view of the stator core 71 particularlyshowing the group 72 in FIG. 8 as an example. Now, FIG. 9 will bedescribed. At the circumferential ends of the tip end 81 of the statortooth 72 a (that is part of the stator core 71) on the opposite side tothe stator yoke, cut parts 83 and 84 are formed so that the rotoropposing surface at the tip end 81 of the stator tooth 72 a that opposesthe stator opposing surface 82 of the rotor 78 is apart from the statoropposing surface 82 of the rotor 78 in the vicinity of thecircumferential ends. Note that the cut parts 83 and 84 are preferablyformed to have substantially the same size. The tip ends of all thestator teeth are formed in the same shape to form the stator core 71. Asthe tip ends of the stator teeth have this shape, abrupt changes in themagnetic field at the stator teeth will be alleviated, so that thewaveform of counter electromotive voltage will be more approximated to asine waveform, and torque ripple and cogging torque will be reduced.

It is understood that when the shape and positioning of the stator teethare the same as those of the stator teeth according to the Embodiment 2described above, the same effects as those brought about by theEmbodiment 2 will be provided.

As in the foregoing, according to Embodiment 3, the stator teeth formingthe stator core are formed so that the rotor-opposing surface at the tipend of the stator tooth has a shape that is apart from thestator-opposing surface of the rotor near the circumferential ends atthe tip end. In this way, abrupt changes in the magnetic field isalleviated, therefore a high torque will be generated, and the waveformof the generated voltage will be approximated to a sine waveform. Torqueripple and cogging torque are reduced, and distortions in the generatedvoltage are reduced. Consequently, the iron loss will be reduced, and avery efficient motor will be provided.

Embodiment 4

FIG. 10A is a schematic top view of a stator core for use inillustration of a motor according to Embodiment 4 of the presentinvention.

As shown in FIG. 10A, a stator core 91 includes stator teeth 92 a, 92 b,92 c, 93 a, 93 b, 93 c, 94 a, 94 b, and 94 c and a stator yoke 95 thatconnects the stator teeth 92 a to 94 c at one end. Similarly to theEmbodiment 1 described above, the stator teeth 92 a to 94 c are dividedinto three groups 92, 93, and 94. The directions in which coils (notshown) are wound around adjacent stator teeth in the same group areopposite, and the relation between the angle h of a slot opening betweenadjacent stator teeth in the same group and the angle H of a slotopening formed between adjacent stator teeth belonging to differentgroups satisfies the foregoing expression (1). In addition, a permanentmagnet-embedded rotor (not shown) opposes the rotor-opposing surfaces ofthe stator teeth 92 a to 94 c with a very small gap therebetween.

Here, the stator teeth in the group 92 will be detailed.

At the surface of the stator tooth 92 b opposing the rotor (not shown)in the center of the group 92 at the tip on the opposite side to thestator yoke 95, a substantially rectangular recess 96 is formed so thatthe circumferential length of the rotor-opposing surface isapproximately divided into three. The recess 96 formed at the statortooth 92 b apparently behaves as if it serves as the N pole when thestator tooth 92 b is for example excited to the S pole by the coil (notshown) arranged around the stator tooth 92 b. Therefore, the magneticpole at the tip end of the stator tooth 92 b is divided into parts withmagnetic poles of S, N, and S in appearance by the recess 96. A recessidentical to that provided in the stator tooth 92 b is each formed inthe stator teeth 93 b and 94 b in the center of the other groups 93 and94, respectively, and the magnetic pole at the tip end is divided intoparts with magnetic poles of S, N, and S in appearance. In this way,high torque is generated, and torque ripple is reduced to a small level.

Note that the number of recesses provided for each stator tooth is notnecessarily one, and as shown in FIG. 10B, two recesses 98 a and 98 bare formed at the tip end of the stator tooth 97 or the number of therecesses may be three or more. The shape of the recess is notnecessarily a rectangular shape. As shown in FIG. 10C, the recess is forexample an arc recess 99 or a plurality of such arc recesses may beprovided. It is understood that the same recess may be provided in theother stator teeth rather than the stator tooth in the center of each ofthe group.

It is understood that when the positioning of the stator teeth the sameas that of the stator teeth according to the Embodiment 2 describedabove is employed or the shape of tip end the same as that according tothe Embodiment 3 may be applied as the shape of the stator teethaccording to the Embodiment 3, the same effects will be provided.

In the description of the Embodiments 1 to 4, the motor is an innerrotor type motor, in other words, the rotor is provided inside thestator, but the same effects will be provided if the motor is an outerrotor type motor, in other words, if the rotor is provided outside thestator.

As in the foregoing, according to Embodiment 4, a recess provided ineach of the stator teeth in the center of the three groups allows areluctance torque to be used in addition to the magnet torque similarlyto the Embodiment 1, so that a high torque is generated, and torqueripple is reduced as well. Furthermore, distortions in the generatedvoltage are reduced, the iron loss is then reduced, and the permanentmagnets are kept from being demagnetized. In this way, a very efficientmotor will be provided.

Embodiment 5

FIG. 11 is a schematic top view of a stator core for use in illustrationof a motor according to Embodiment 5 of the present invention.

As shown in FIG. 11, a stator core 101 includes stator teeth 102 a, 102b, 102 c, 103 a, 103 b, 103 c, 104 a, 104 b, and 104 c, and a statoryoke 105 that connects these stator teeth 102 a to 104 c at one end.Similarly to the Embodiment 1 described above, the stator teeth 102 a to104 c are divided into three groups 102, 103, and 104. A slot 106 as aspace for arranging a coil (not shown) around is formed each betweenadjacent stator teeth among the stator teeth 102 a to 104 c. The sidesurfaces 102 aL and 102 aR of the parallel part of the stator tooth 102a and the side surfaces 105 aL and 105 aR of the stator yoke 105 coupledwith the aforementioned surfaces are substantially at right angles sothat the coil is wound around stator tooth 102 a in a regular windingmanner in order to maximize the number of turns in a coil for a slotspace. The side surfaces of the parallel parts of the stator teeth 102 bto 104 c and the side surfaces of the stator yoke 105 on the rotor sideare substantially at right angles similarly to the stator tooth 102 a.The side surface 105 aR and the side surface 105 bL on the rotor side ofthe stator yoke 105 intersect at a intersection 105 ab, have a flat,substantially V shape and together form a side surface 107 of the statoryoke 105 on the rotor side forming the slot 106. An outer side surface107 s opposing the side surface 107 of the stator yoke 105 on the rotorside is parallel to both the side surfaces 105 aR and 105 bL of thestator yoke 105 on the rotor side, and lines in contact with the outercircumference of a circle 110 centered on the center O of the rotorrotating shaft form side surfaces 107 aR and 107 bL. Note that in thiscase, an intersection 108 a where the surfaces 107 aR and 107 bL in theside surface 107 s parallel to the side surfaces 105 aR and 105 aL,respectively intersect each other is rounded in shape.

Meanwhile, the side surface 109 of the stator yoke 105 on the rotor sidein the slot 106 between the adjacent stator teeth 103 a and 104 cbelonging to the adjacent groups 103 and 104 is formed by side surfaces105 aL and 105 cR having a length substantially equal to the length ofthe above described side surface 105 aR and a side surface 105 cconnecting these side surfaces 105 aL and 105 cR. Here, the outer sidesurface 109 s relative to the side surface 109 of the stator yoke 105and positioned opposite to the slot 106 is formed by a side surface 109aL parallel to the side surface 105 aL of the stator yoke 105 and incontact with the outer circumference of the circle 110 centered on thecenter O of the rotor rotating shaft, a side surface 109 cR parallel tothe side surface 105 cR of the stator yoke 105 and in contact with theouter circumference of the circle 110 centered on the center O of therotating shaft and a side surface 109 c parallel to the side surface 105c. At the time, the distance between the side surfaces 105 c and 109 cis set to be the same as the distance between the side surfaces 105 aLand 109 aL (and also the same as the distance between the side surfaces105 cR and 109 cR). In this way, the side surface 107 aR in the aboveside surface portion 107 s and the side surface 109 aL in the sidesurface portion 109 s are aligned. Note that the intersection 108 bwhere the side surfaces 109 aL and 108 c intersect and the intersection108 c where the side surfaces 109 cR and 109 c intersect may be roundedin shape similarly to the intersection 108 a.

The side surfaces of the stator yoke on the opposite side to the rotoropposing the slots formed between the stator teeth are formed similarlyto the above described manner, and the width w of the stator yoke issubstantially equal for the entire circumference. At the time, therelation between the width w of the stator yoke and the width W of theparallel part of the stator teeth is preferably in the range expressedas follows:W×½≦w≦W× 3/2

In addition, the side surface portions 107 s and 109 s of the statoryoke 105 on the opposite side to the rotor (not shown) side opposing theslot 106 protrude toward the opposite side (outer side in the radialdirection) to the rotor side from the circle 110 centered on the centerO of the rotating shaft inscribed on the side surfaces of the statoryoke 105 on the opposite side to the rotor side in the stator teeth 102a to 104 c.

In this way, the side surfaces 107 s and 109 s of the stator yoke 105 onthe opposite side to the rotor side protrude in the direction oppositeto the rotor corresponding to the slots 106. The width w of the statoryoke is substantially equal for the entire circumference, so that themagnetic resistance will be well balanced, and a substantiallyhomogeneous magnetic flux will be generated. Consequently, a stable andefficient magnetic field will be provided.

Using the above-described stator core 101, a plurality of stator teeth102 a to 104 c forming the stator core 101 are divided into threegroups, and the coils (not shown) are wound in the opposite directionsaround adjacent stator teeth belonging to the same group. The relationbetween the angle h of a slot opening between adjacent stator teeth inthe same group and the angle H of a slot opening formed between adjacentstator teeth belonging to different groups satisfies the foregoingexpression (1). In addition, a permanent magnet-embedded rotor (notshown) is opposed against the inner circumferential surfaces of thestator teeth 102 a to 104 c with a very small gap therebetween similarlyto the Embodiment 1 as described above.

It is understood that the shape and positioning of the stator teeth inthe stator cores according to the Embodiments 2 to 4 as described abovemay be applied.

It is also noted that the configurations of the stators and rotors inthe Embodiments 1 to 5 described above allow voltage having asubstantially sine waveform to be generated when the rotor is driven torotate as is well known, so that an efficient generator is provided.

As in the foregoing, according to Embodiment 5, the plurality of statorteeth 102 a to 104 c and the stator yoke 105 whose width issubstantially equal form the stator core 101, so that the magneticresistance is well balanced, a substantially homogeneous magnetic fluxwill be generated, and a stable and efficient magnetic field will beprovided. Similarly to the Embodiment 1 described above, a high torqueis generated and distortions in the generated voltage are reduced toreduce the iron loss, which prevents the permanent magnets from beingdemagnetized. Therefore, a very efficient motor will be provided.

Embodiment 6

Now, Embodiment 6 will be described.

The motor according to the above described embodiments of the presentinvention are inner rotor type motors for the ease of illustration,while with an outer rotor type motor, the same effects are broughtabout. An outer rotor type motor according to this embodiment is shownin FIG. 12. The positional relation between the rotor and stator isreversed and the other configuration is basically the same. The outerrotor type motor cannot be formed into a large size machine, but theopening of the stator around which a coil is arranged faces outwardlyand therefore winding the coils around becomes easier, which is suitablefor mass production.

FIG. 12 shows a stator 110 and groups 111, 112, and 113 each having aplurality of stator teeth with coils wound around and supplied withvoltage in the same phase, outer rotor type magnets 114, a fixed frame115 for the magnets, and a rotor 116 including the magnets 114 and thefixed frame 115. The frame 115 typically serves as a magnet yoke. Thegroups of stator teeth 111 a, 111 b, and 111 c, 112 a, 112 b, and 112 c,and 113 a, 113 b, and 113 c correspond to the above three groups, i.e.,the U, V, and W phases, respectively. Here, the stator 110 is coupled toa plate for fixation with the outside, and the rotor 116 is rotatablycoupled to the stator 110 through a shaft and a bearing. The numeral 117represents a stator coil.

It is understood that in connection with FIG. 12, a magnet embedded typeconfiguration, in other words, an IPM motor is described as an exampleof an inner rotor type motor, but a surface magnet type motor, in otherwords, an SPM motor may similarly be applied.

Embodiment 7

Now, Embodiment 7 of the present invention will be described.

In the above description, the motor is a brushless type motor by way ofillustration, but a brush commutator motor may similarly be applied, andthe same effects as those by the above-described embodiments are broughtabout. The present embodiment is exactly the case. The brush commutatormotor has a similar configuration as that of an outer rotor brushlessmotor, and typically includes magnets on the outer side and a statorhaving coils on the inner side. However, unlike the outer rotorbrushless motor, according to the present embodiment, the rotating partis on the coil side positioned on the inner side, and therefore amechanism to feed the coil through the brush commutator is necessary. Anexample of an SPM brush commutator motor having the above-describedconfiguration is shown in FIG. 13.

FIG. 13 shows a rotor 118, groups 119, 120, and 121 each having aplurality of stator teeth with coils wound around and supplied withvoltage in phase, magnets 122, a fixed frame 123 for the magnets, and astator 124 including the magnets 122 and the frame 123. The frame 124typically serves as a magnet yoke. The groups of stator teeth 118 a, 118b, and 118 c, 119 a, 119 b, and 119 c, and 120 a, 120 b, and 120 ccorrespond to the above three groups, i.e., the U, V, and W phases,respectively. There are a feeding brush 126, a commutator 127, arotating shaft 128, a brush retainer 129, and a feeding line 130. Thestator 124 is coupled with a plate (not shown) for fixation with theoutside, and the rotor 118 is rotatably coupled to the stator 124through the rotating shaft 128 and a bearing (not shown).

Embodiment 8

Now, Embodiment 8 of the present invention will be described.

The use of aluminum or an aluminum alloy for coils to reduce the weightof a motor is generally practiced. When a copper coil for a motor is tobe changed to an aluminum coil in general, the stator rotor part must belarger in size than the copper wire motor about by 26% so that the motortemperature rise is unchanged, because the resistance value of thealuminum coil is about 1.6 times as large as that of the copper coil.The motor according to the present invention is designed to have atorque per volume about twice as high as a typical motor, and thereforeeven using an aluminum or aluminum alloy coil, the motor will be smallerin size than other motors with copper coils. Therefore, the volume, theweight, and the cost will be reduced.

An aluminum or aluminum alloy coil has poor solderability. Therefore, inorder to compensate for the disadvantage, according to the presentembodiment, an aluminum or aluminum alloy coil is coated with a metalfree from copper and having good solderability such as iron, nickel,zinc, tin, and silver, a combination of at least two of these metals, oran alloy containing or any of these metals as a main component.

FIG. 14 shows a section of the aluminum or aluminum alloy coil. Thefigure shows an aluminum or aluminum alloy coil 131 that is a main partof the motor coil, a metal 132 such as iron, nickel, zinc, tin, andsilver, a combination of at least two of these metals, or an alloycontaining any of these metals as a main component, and an insulatingcoating film 133.

The above described metal or alloy may cover only the end part of thealuminum or aluminum alloy wire when the wire is wound around for themotor. The metal or alloy may be fixed to the aluminum or aluminum alloywire before or after winding by shrink-fit or caulking. The metal oralloy having an arc or polygonal section may be disconnected in theaxial direction. The metal covering the aluminum or aluminum alloy wireneeds only cover the coil coupling end as it suits the purpose, andtherefore the metal or alloy may be shrink-fit or caulked for fixing tothe end when coils are wound around for the motor. An example of thiswill be described in conjunction with FIGS. 15A and 15B. FIGS. 15A and15B show a metal ring 134 a fixed by shrink-fit, a metal ring 134 bfixed by caulking, and its caulked part 135. Note that the metal memberdoes not have to be in such a continuous ring shape, and the same effectwill be provided if there is a disconnection in the ring partly orentirely in the axial direction.

Embodiment 9

Now, Embodiment 9 of the present invention will be described.

Most brushless motors store a circuit board for a driving circuit.Therefore, according to Embodiment 9, a metal other than typical copperand having good solderability as described in conjunction with the aboveembodiment is used for the metal for interconnection for the circuitboard. In this way, a circuit board built-in brushless motor having asmaller size than the other configuration and completely free fromcopper will be provided. When a brush commutator motor is used, the useof a motor completely free from a copper component typically included ina brush commutator completely removes the motor of copper. As for amotor having a connector, the use of a metal completely free from copperallows a completely copper-free motor to be provided.

Embodiment 10

Now, Embodiment 10 of the present invention will be described.

Some motors have a lead wire and the lead wire must be made of analuminum or aluminum alloy wire in order to provide a completelycopper-free motor. In this case, an aluminum or aluminum alloy wirehaving its surface coated with a metal having good solderability or ametal free from copper and having good solderability is attached to theends by caulking or shrink fit. Similarly to the above-describedembodiments, the metal member needs only have a cylindrical or polygonalsection, and may be disconnected in the axial direction.

FIGS. 16A to 16C show aluminum or aluminum alloy wires 136 coated with ametal as described above that are used as a lead wire for feeding themotor. Here, 137 is an insulating coating, and 138 is an aluminum wirecoated with 132 or 134 a, and 134 b and soldered at a winding solderportion 139. The numeral 140 indicates a core of the aluminum oraluminum alloy lead wire, 141 is a metal ring with good solderabilityfixed to the core wires 140 by caulking or shrink fit, and 142 is acaulking ring for fixing the core wires 140 of the aluminum or aluminumalloy wires and the coil 138.

Note that in the foregoing, the aluminum or aluminum alloy wire isdescribed by way of illustration, but a metal or an alloy other thanaluminum may be employed as long as a copper wire is not used.

As in the foregoing, the Embodiments 1 to 10 are described. Note thatthe motor generator according to the Embodiments 1 to 10 are also usefulas a motor for driving a vehicle such as PEV (Pure Electric Vehicle),HEV (Hybrid Electric Vehicle), and FCEV (Fuel Cell Electric Vehicle), sothat there is no necessity for providing two kinds of motor generatorsfor a high pressure system and a low pressure system or for separatelyproviding a DC—DC converter as would otherwise be done according to theconventional technique. Therefore, an electric vehicle driving systemwith a reduced space will be provided at a reduced cost, so that anelectric vehicle whose compartment is spacious will be provided lesscostly. This also applies when the motor is used as a motor provided ina home electrical appliance or a robot for driving the appliance orrobot, and the same effect will be brought about.

INDUSTRIAL APPLICABILITY

As in the foregoing, according to the present invention, a high torqueis generated for a permanent magnet-embedded type, concentrated windingmotor, and since coils for adjacent stator teeth in each group of statorteeth have different polarities from each other, the magnetic fielddistribution deviations and distortions in voltage generated betweenterminals at the time of driving the motor are reduced. Eddy current isreduced so that the iron loss is reduced. Since heat generation by eddycurrent at the permanent magnets is reduced, the demagnetization of thepermanent magnets is also reduced. Consequently, a highly efficientmotor is provided.

In addition, the motor is free from a copper wire for motor coils, has amotor volume smaller than a typical copper wire motor and reduceddistortions in inductive voltage waveform. Therefore, a motoradvantageous in terms of resource conservation is provided, and themotor is useful for reducing copper wires for an engine built-in motorfor a hybrid vehicle, a main power motor for an electric vehicle, andvarious other motors for a vehicle such as a motor for air conditioning.

1. A motor, comprising: a stator including a stator core having aplurality of stator teeth, and a stator yoke that connects the pluralityof stator teeth, and coils wound around the plurality of stator teeth;and a rotor including a rotor core, and a plurality of permanent magnetsembedded in said rotor core, wherein the plurality of adjacent statorteeth around which the coils are wound around are provided in groups,said coils being provided with in phase voltage, the coils being woundin opposite directions around the plurality of adjacent stator teeth inthe same group, and voltages in different phases being applied toadjacent groups of stator teeth, wherein slot openings are providedbetween each of the adjacent stator teeth, the slot openings betweenadjacent teeth of the same group having a different spacing than slotopenings between adjacent teeth of different groups.
 2. The motoraccording to claim 1, wherein there are 3s groups where s is a positiveinteger, and each said group includes n stator teeth where n is apositive integer.
 3. The motor according to claim 2, wherein when thenumber of poles of said rotor is p, the total number of said statorteeth is t, and the number of sets of coils is s when coils in threephases, U, V, and W phases are set as one set where p, t, and s are eacha positive integer, the relation represented by the following expressionis satisfied:p=2×(s(±1+3k)) and p>t where k is a positive integer.
 4. The motoraccording to claim 3, wherein the relation between an angle h of theslot opening formed between adjacent stator teeth in the same group andan angle H of the slot opening formed between adjacent stator teethbelonging to different groups is represented by the followingexpression:h<H≦3h.
 5. The motor according to claim 1, wherein a central linepassing through each of the circumferential centers of the tip ends ofstator teeth in each group positioned at both ends of said groupadjacent to the stator teeth belonging to different groups is deviatedin the circumferential direction from a central line passing througheach of the circumferential centers of parallel parts of the statorteeth positioned at both ends in said group.
 6. The motor according toclaim 5, wherein the circumferential ends at the tips of stator teethpositioned at both ends in each said group are not positioned inward, inthe width-wise direction of the parallel parts of stator teethpositioned at both ends in said group.
 7. The motor according to claim1, wherein at said plurality of stator teeth that form the stator core,in the vicinity of the circumferential end of the tip end of the statortooth that opposes the stator opposing surface of the rotor, cut partsare provided spaced from the stator opposing surface of the rotor. 8.The motor according to claim 1, wherein the tip end of one or more ofthe plurality of stator teeth forming said group on the side of saidrotor is provided with one or more recesses.
 9. The motor according toclaim 8, wherein said recess is one of a rectangular shape and an arcshape.
 10. The motor according to claim 1, wherein a side surface ofsaid stator yoke on the side opposite to the rotor side in said statorprotrudes more onto the side opposite to the rotor side beyond a circlehaving a radius extending from the center of the rotating shaft of themotor to a side surface of each of said plurality of stator teeth on theside opposite to the rotor side, and a width w of the stator yokecoupling said plurality of stator teeth is equal for the entirecircumference of said stator core.
 11. The motor according to claim 10,wherein the relation between the width w of said stator yoke and a widthW of the parallel part of said stator tooth around which a coil is woundis represented by the following expression:W×½≦w≦W× 3/2.
 12. The motor according to claim 1, wherein said rotor isa surface magnet type rotor.
 13. The motor according to claim 1, whereinsaid rotor is a magnet-embedded type rotor.
 14. The motor according toclaim 1, wherein the rotor core includes a plurality of slits havingsubstantially the same shape as that of the plurality of permanentmagnets provided in said rotor on the opposite side to the stator sideof said plurality of permanent magnets, and a width of said slits aresmaller than the thickness of said permanent magnets.
 15. The motoraccording to claim 1, wherein in said rotor comprising said plurality ofpermanent magnets, a distance between the stator side surface of each ofsaid plurality of permanent magnets and a stator opposing surface ofsaid rotor is larger toward the central part than at the ends of each ofthe permanent magnets.
 16. The motor according to claim 15, wherein saidplurality of permanent magnets forming said rotor are in a substantiallyV shape that protrudes in a direction opposite to the side of the statoropposing surface of said rotor.
 17. The motor according to claim 15,wherein said plurality of permanent magnets forming said rotor are in alinear shape arranged perpendicularly to the radial direction of saidrotor.
 18. The motor according to claim 15, wherein said plurality ofpermanent magnets forming said rotor are in an arc shape that protrudesin a direction opposite to the side of the stator opposing surface ofsaid rotor.
 19. The motor according to claim 15, wherein said pluralityof permanent magnets forming said rotor are in an arc shape thatprotrudes to the side of the stator opposing surface of said rotor andhas a larger radius than the radius of said rotor core forming saidrotor.
 20. The motor according to claim 3, wherein each said groupincludes three stator teeth, and the total number of the stator teeth is9s, and the number of rotor poles p is 10s.
 21. The motor according toclaim 1, wherein said rotor is in an outer rotor structure.
 22. Themotor according to claim 1, wherein said rotor is provided with anarmature coil, and said armature coil is fed through a brush and acommutator.
 23. The motor according to claim 1, wherein aluminum wire oraluminum alloy wire-is used as an armature coil.
 24. The motor accordingto claim 1, wherein aluminum wire or aluminum alloy wire having asurface coated with a metal or alloy with solderability is used as anarmature coil.
 25. The motor according to claim 1, wherein aluminum wireor aluminum alloy wire having an end surface coated with a metal oralloy with solderability is used as an armature coil.
 26. The motoraccording to claim 25, wherein in the aluminum wire or aluminum alloywire having the end surface coated with said metal or alloy withsolderability, said metal or alloy with solderability is fixed bycaulking or shrink fit.
 27. The motor according to claim 1, furthercomprising a built-in circuit board, wherein any one of iron, nickel,zinc, tin, silver, a combination of two or more of these metals, and analloy containing any of these metals as a main component is used for aninterconnection pattern for said circuit board.
 28. The motor accordingto claim 22, wherein any one of iron, nickel, zinc, tin, silver, acombination of two or more of these metals, an alloy containing any ofthese metals as a main component, a mixture of any of these metals andcarbon, and carbon is used for the brush or the commutator.
 29. Themotor according to claim 1, further comprising a connector made with anyone of iron, nickel, zinc, tin, silver, a combination of two or more ofthese metals, and an alloy containing any of these metals as a maincomponent.
 30. The motor according to claim 1, wherein aluminum wire oraluminum alloy wire having an end coated with a metal or alloy withsolderability is used as a feeding lead wire.
 31. The motor according toclaim 1, wherein aluminum wire or aluminum alloy wire having a metal oralloy with solderability fixed to an end by caulking or shrink fit isused as a feeding lead wire.
 32. The motor according to claim 24,wherein said metal or alloy with solderability is any one of iron,nickel, zinc, tin, silver, a combination of two or more of these metals,and an alloy containing any of these metals as a main component.
 33. Avehicle comprising the motor according to claim 1 as a vehicle drivingmotor.
 34. A hybrid vehicle comprising the motor according to claim 1 asa vehicle driving motor.
 35. An electric vehicle comprising the motoraccording to claim 1 as a vehicle driving motor.
 36. A fuel cellelectric vehicle comprising the motor according to claim 1 as a vehicledriving motor.
 37. A home electrical appliance comprising the motoraccording to claim 1 as a driving motor for the appliance.
 38. A robotcomprising the motor according to claim 1 as a driving motor.
 39. Themotor according to claim 25, wherein said metal or alloy withsolderability is any one of iron, nickel, zinc, tin, silver, acombination of two or more of these metals, and an alloy containing anyof these metals as a main component.
 40. The motor according to claim26, wherein said metal or alloy with solderability is any one of iron,nickel, zinc, tin, silver, a combination of two or more of these metals,and an alloy containing any of these metals as a main component.
 41. Themotor according to claim 30, wherein said metal or alloy withsolderability is any one of iron, nickel, zinc, tin, silver, acombination of two or more of these metals, and an alloy containing anyof these metals as a main component.
 42. The motor according to claim31, wherein said metal or alloy with solderability is any one of iron,nickel, zinc, tin, silver, a combination of two or more of these metals,and an alloy containing any of these metals as a main component.